Carotid endarterectomy (CEA), surgery to prevent stroke, is common but potentially risky. Randomized controlled trials (RCTs) showed that among carefully selected patients (Pts) and surgeons, CEA reduced the risk of death and stroke compared to medical therapy. However, symptomatic Pts (with strokes or transient ischemic attacks) needed to survive for 2-3 years to realize the benefits of CEA, and asymptomatic patients needed to survive for 5 years to benefit. Because Pts undergoing CEA in community practice are older and sicker than those in the RCTs and have shorter life expectancy, the benefits of CEA for these Pts may be more limited. The potentially reduced benefit of CEA would be most marked among asymptomatic Pts who comprise three-quarters of those having the procedure. Despite its, widespread use, the long term outcomes of CEA in community practice and the relative benefits of CEA v. medical therapy in the elderly is unknown. The specific aims of this application are to: 1) Determine the generalizability of the CEA RCTs by comparing the long term outcomes of CEA performed in community practice using the population-based, New York Carotid Artery Surgery (NYCAS) Medicare cohort study to those reported in the RCTs;2) Assess the effectiveness of surgical (CEA) v. medical management of carotid disease among the elderly in community practice using 2 methods: 2A) Comparing long term outcomes of Medicare Pts who underwent CEA in NYCAS to similar Pts with carotid disease in the population-based Cardiovascular Health Study (CHS) who did not have surgery;and 2B) Comparing long term outcomes of elders with carotid disease in CHS who were surgically (CEA) v. medically managed using propensity score methods;3) Examine differences in long term outcomes of CEA in the elderly according to: age, comorbidities, RCT eligibility, gender, race/ethnicity, and symptom status, and develop and validate a multivariate clinical model to predict outcomes;and 4) Identify the independent process of care, surgeon, and hospital factors that influence risk-adjusted, stroke- specific survival to inform best practices and policies. NYCAS has detailed Pt, clinical, process, surgeon, and hospital data. Deaths and strokes 5 and 10 years after CEA for 4000 NYCAS Pts will be assessed using the National Death Index and performing chart review of stroke admissions identified by Medicare Part A claims. CHS has detailed clinical baseline and long term outcomes data. Outcomes in NYCAS will be compared to the RCTs. Long term outcomes of 418 CHS Pts with carotid disease who were medically managed will be compared(1:4) in matched analysis to 1672 similar NYCAS CEA Pts ('Between Study'analysis). In a 'Within Study'analysis, 69 CHS Pts who had CEA will be compared to 418 who were medically managed using propensity scores. Multivariate regression will be used to identify Pt, process of care, surgeon, and hospital predictors of long term outcomes in NYCAS (N=4000).